Surgical instruments are often transported in a box-like tray having a bottom wall and upstanding side and end walls all of which have vent holes. Prior to use, the instruments are placed in the tray and subjected to sterilization under pressure. Following sterilization, the tray full of instruments may be transported to an operating room and placed close to the surgical team whose members may withdraw the instruments from the tray as needed for the particular surgical procedure being performed. Usually, the instruments are selectively arranged in the tray so that the instruments can be picked from the tray in the order that they are needed for the particular surgical procedure.
During sterilization a substantial amount of steam accumulates in the tray. At the end of the sterilization process as the pressure drops, this water vaporizes. The heat to vaporize the water is mainly from conduction in the tray. Also, a drying time may be included at the end of sterilization. During this time, heat radiates from the sterilizer walls to the tray and is conducted through the tray walls to vaporize any residual water in the tray. Therefore to minimize the sterilization time, it is important that the tray be thermally conductive.
For this reason, the sterilization trays have historically been made entirely of a metal such as stainless steel or aluminum. It is easy to stamp and fold sheet metal to form a tray. However, it is extremely difficult, if not impossible, to produce a tray with rounded corners in this fashion. Round corners are desirable because the trays are often wrapped in anti-microbial paper or plastic jackets and during such handling any sharp corners might tear the jackets. Trays with rounded corners can be produced by a drawing process. However, the dies for doing this are very expensive so that the unit cost of such drawn metal trays is quite high.
Because of such cost considerations, the medical products industry has in recent years resorted to making sterilization trays with rounded corners entirely out of a plastic material able to withstand the sterilization temperatures. Unfortunately however, the plastic materials used for this purpose have relatively low thermal conductivity. Therefore, the tray actually acts as a thermal barrier. As a result, it takes longer to sterilize the instruments than would be the case if the instruments were supported in a metal tray.